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    Re: Santa Barbara 2016: Venus sight
    From: Stan K
    Date: 2016 Dec 19, 12:28 -0500

    I've been trying to send this privately, both on and off NavList, but the messages keep getting returned.  I thought you might have changed you address because of the Yahoo hack, but your messages seem to be coming from the same old address.

    Anyway, I have a question about the way Astron defines twilights.  All the definitions of twilight, whether civil or nautical (or astronomical) that I can find involve the sun, rise or set.  Morning twilight starts at the start of AM nautical/civil twilight and ends at sunrise.  Evening twilight starts at sunset and ends at the end of civil/nautical twilight.  Astron seems to define AM twilight as starting from the start of AM nautical twilight and ending at the start of AM civil twilight; PM twilight starts at the end of PM civil twilight and ends at the end of PM nautical twilight.

    If there is a reference that defines twilights this way, please let me know what it is.


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